Wood lagging has been traditionally used for earth retention in applications such as retaining walls, drainage, mine shoring; for insulating layer between the boiler and jacket on steam locomotives, and for pipe casing. To date lagging has been manually assembled at the application site, or manufactured at an off site factory. In applications where long lengths of pipe need to be protected, the automated manufacture of lagging can reduce logistics and labour costs.
Automatic manufacture of lagging requires that lumber of some dimension is placed one board adjacent to another with a gap spacing between them such that when wrapped around a pipe of a given dimension that the lagging blanket ends meet with the same gap. Singulating lumber from a deck or pile and introducing the singulated piece into a lugged transfer is well documented in the following patents:
U.S. Pat. No. 5,921,376 titled “High speed revolving lug loader with retracting heel and hook”, issued to Steven W. Michell et al on Jul. 13, 1999 describes a high speed revolving lug loader with retracting heel and hook in which presented boards are grasped by pinching the top and bottom surfaces between a heel and hook travelling on the circumference of a number of disks located along the length of the board and situated between the smooth and lugged conveyors. Again this does not allow for accurate and variable gapping between boards.
U.S. Pat. No. 4,869,360 titled “Lug loader”, issued to Douglas J. Brown et al on Sep. 26th, 1989 describes a lug loader in which a ducking stop allows one board at a time onto a speed up conveyor transferring the singulated board onto a lugged conveyor, and timed such that the singulated board is transferred on between lugs. Again this is not applicable in the present invention where accurate and variable gap control is required.
U.S. Pat. No. 3,989,135 titled “Apparatus for single feeding timber”, issued to Niilo Pyykonen on Nov. 2, 1976 describes an apparatus for single feeding timber from a single layer mat by lifting a stopped board from one conveyor onto another using elevated flights on a transfer conveyor and placing the boards onto a lugged conveyor. This technique does not lend itself to variable gap control between boards.
Similarly the Applicant is aware of patents regarding the de-stacking of lumber as documented in the following patents:
U.S. Pat. No. 6,379,105 titled “Automatic Lumber Unloading and Feeding Apparatus”, issued to Aylsworth on Apr. 30th, 2002 describes an automatic lumber unloading and feeding apparatus that separates individual boards from a stacked unit using a pair of pushers to push the bottom tiers off of a supporting surface onto a conveyor below. The tier is then singulated by lifting all of the tier boards except for the first one simultaneous with a lifting gate that allows the singulated board to flow along the conveyor. This is more complicated than the present invention, lifting a mass of boards instead of one, and does not provide the means to accurately gap trailing to leading boards, which is fundamental to the present invention. It is also limited to a single width of board.
U.S. Pat. No. 743,075 title “Hoop or Band for Cylindrical Casings issued to Hammond on Nov. 3, 1903 teaches a hoop comprising a band with bent ends and a stave coupler to secure cylindrical casings made of lumber about pipe. This would typically require the lumber to be placed about the pipe, held by some secondary means and then secured with Hammond's invention. This approach is labor intensive and awkward to implement, requiring the casing to be built and retained in place around the pipe.
U.S. Pat. No. 4,405,276 titled “Apparatus for unstacking planks”, issued to Karl-Wolfram Wiegand on Sep. 20, 1983 describes an apparatus for longitudinally pushing individual boards one at a time from the top tier of a stack using a traverse truck. The elevation of the stack is optimized using a scissor lift such that only the top tier clear a back stop opposing the direction of the truck travel, holding the lower tiers in place. As Wiegand does not disclose how the longitudinally singulated plank is landed or oriented in the downstream process it does not teach how to place planks adjacent to each other with a variably controlled gap for forming pipe casing or lagging.
Applicant is aware of automated stapling of straps to boards in the fabrication of bed frames, however in this instance the boards are placed in a fixed displacement lugged transfer by means of a lug loader, and straps are applied with automatic staplers.
Nowhere in the prior art is there taught a method for singulating lumber and precisely placing it adjacent to previously singulated board with a fixed but variable gap for any purpose, let alone forming the boards into a pipe casing, or lagging blanket.